High-density natural active sites for efficient nitrogen reduction on Kagome surfaces promoted by flat bands

Abstract

Recent studies have shown that single- or few-atom catalysts, with local states near the Fermi level, can promote nitrogen activation and the entire electrocatalytic nitrogen reduction reaction (eNRR) process, but are facing limitations in loading densities and stability. Here, we conceptualize that the Kagome metals featuring naturally abundant surface sites and flat bands are promising candidates to catalyze eNRR. Using first-principles calculations, we first show that the Kagome termination of the prototypical FeSn is accompanied by the presence of flat bands from the Fe-d_z² and d_xz/d_yz orbitals, and the exposed surface can strongly chemisorb N₂ with an adsorption energy of ~−0.7 eV. The limiting potential of 0.31 V indicates superior eNRR catalytic activity. The mutual independence between neighboring reactive sites also ensures an exceptionally high 25% atomic utilization within the Kagome layer, with each active site possessing high selectivity of eNRR. Our detailed analysis further reveals the critical role of the flat bands in boosting catalytic activity, which is also generalized to the isostructural CoSn and FeGe Kagome systems. Collectively, this work not only enhances the functionalities of Kagome materials for applications but also integrates flat band physics with single-atom catalysis, offering new opportunities in catalyst design.